What Is Sett and Why It Matters
Sett (also called EPI — Ends Per Inch) is the number of warp threads per inch of weaving. Getting the sett right is fundamental to the quality of your woven fabric.
Too few ends per inch (open sett) and your fabric will be sleazy — loose, unstable, and prone to shifting. Too many ends per inch (close sett) and your fabric will be stiff, warp-dominant, and difficult to beat evenly.
The right sett depends on two things: the thickness of your yarn and the weave structure you're using.
The WPI Method
The standard way to determine sett is the WPI (Wraps Per Inch) method. Wrap your yarn around a ruler for one inch, laying each wrap snugly next to the last without overlapping or compressing.
Count the wraps. This is your maximum possible sett — the theoretical maximum number of ends you could pack into one inch. Your actual weaving sett will be a percentage of this, determined by your weave structure.
For plain weave: use 50–60% of your WPI. For twill: use 60–70%. For satin: use 70–80%. For lace weaves: use 30–40%.
For example, if your yarn wraps at 12 WPI: plain weave sett = 6–7 EPI, twill sett = 7–8 EPI.
Calculating Warp Length
Your total warp length must account for more than just the finished project length. You need to add loom waste (typically 18–36 inches of warp that can't be woven because it's tied to the loom), sampling length (6–12 inches to test sett and structure before weaving the real project), take-up (the warp gets shorter as it goes over and under weft threads, typically 5–10%), and shrinkage (yarn shrinks when washed, varying by fiber).
Shrinkage by fiber: cotton shrinks about 10%, wool 10–15%, linen 3–5%, silk 5–8%, synthetics 2–3%.
Our Warp Length Calculator adds all of these factors and shows total yardage for both warp and weft.
Reed Substitution
Your reed's dent (spaces per inch) doesn't always match your desired sett. For example, you may want a sett of 15 EPI but only have a 12-dent reed.
The solution is threading multiple ends per dent in some or all dents. For 15 EPI in a 12-dent reed: 15 ÷ 12 = 1.25 ends per dent. Thread 1 end in some dents and 2 in others, alternating to distribute evenly.
The pattern would be: 1, 1, 1, 2, 1, 1, 1, 2, 1, 1, 1, 2 — that's 15 ends in 12 dents. Our Reed Substitution calculator figures this out for any sett and reed combination.